"You know, I sort of don't feel like [my life] has changed that much," Dornan, who shares two kids -- daughters Dulcie, 3, and Phoebe, 1 -- with wife Amelia Warner, told ET's Carly Steel. "The making of these movies coincided with me becoming a father, and I've had two kids in the time we've made these films, so that's changed my life immeasurably."

"I don't know if you have kids, but it is totally life transforming," he continued. "So, in a way it's been great because I sort of, it's been the perfect distraction from what would be changing my life if they hadn't come along -- if it was just about this franchise."

Dornan admitted, however, that there has been one major change to his lifestyle.

"I get recognized probably more than I did four years ago," he said. "But it's nothing crazy. I think I'm quite good at sort of blending in."

He credits part of that reason to Johnson, who he calls a "good friend."

"I was cast very late in the process of making the first [Fifty Shades of Grey] movie," he explained. "By the time we'd started filming, I'd [only] met Dakota a couple of times."

"Now over the years, we've become very close," he said of his co-star. "That helps. We need to be sort of partners going into some of those scenes, and we need to have each other's back and love and respect each other the way we do. We both count ourselves very lucky that we get along so well. You know, it could be so difficult if we didn't see eye to eye. You hear horror stories of actors not getting on well."

Johnson echoed those sentiments, telling ET, "Jamie and I have become so close that [filming the second movie] was like going to work with your friend every day."

The 27-year-old actress explained that there are a lot more sex scenes in Fifty Shades Darker, which hits theaters Feb. 10, so feeling comfortable around Dornan was crucial.

"The story is more intricate, and we got to really explore the characters, and their personalities and their relationship," she dished. "It's truly a conversation, like, 'Well in the last [scene] we shot, I was on my back, so maybe this time you should turn me over.' Or like, it's conversations like that which are so embarrassing and mundane."